A drug giant settled one of the nation’s largest product-liability cases yesterday by agreeing to pay up to $4.83 billion to patients who claimed the fen-phen diet-drug cocktail caused dangerous heart problems.

Under the settlement, American Home Products will set aside $3.75 billion for payments lasting 16 years. With interest, the amount could rise to $4.83 billion.

That surpasses the $3.2 billion that Dow Corning agreed to pay to women who claimed injury from its silicone breast implants.

But the amount is far below the $368.5 billion settlement reached between the tobacco industry and its opponents.

American Home, the nation’s fifth-largest drug maker, will pay $2.32 billion for injuries, $1 billion for drug refunds and medical monitoring and at least $429 million in plaintiffs’ legal fees.

The maker of Advil also will pay $25 million for heart-disease research.

American Home’s payments, which will begin later this year, will range from $30 for prescription refunds to a maximum of $1.5 million per person for those with serious health problems.

“We have truly broken new ground,” said Michael Fishbein of Philadelphia, one of the plaintiffs’ lawyers.

“This agreement ensures that all class members will be treated with parity and fairness,” said Stanley Chesley of Cincinnati, another of the lawyers.

Up to 6 million Americans used the diet-drug mix before it was yanked off the market in 1997. Subsequently, 6,500 separate suits were filed against American Home.